Foreword
Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This document is developed in accordance with the rules given in GB/T 1.1-2020 Directives for standardization - Part 1: Rules for the structure and drafting of standardizing documents.
This document replaces GB/T 18604-2014 Measurement of natural gas flow by gas ultrasonic flow meters. In addition to structural adjustments and editorial changes, the following main technical changes have been made with respect to GB/T 18604-2014:
a) Natural gas flow measurements in "standard facility of measurement and other application places" are added. “This document may serve as a reference for the measurement of natural gas flow by clamp-on gas ultrasonic flow meters” is deleted (see Clause 1 hereof; Clause 1 of Edition 2014);
b) Contents about “parameters” in Clause 3 are deleted (see 3.1 of Edition 2014);
c) The following terms are deleted: velocity sampling interval, flow calibration factor, and maximum error shift with one path failed (see 3.2.12, 3.2.16 and 3.2.17 of Edition 2014);
d) "Natural gas composition" is added (see 4.2.2 hereof; 4.2.2 of Edition 2014);
e) The following is deleted: "Under normal gas transmission working conditions, the attachments in the meter body (such as condensate or oil residues with processing impurities, dust and sand) will reduce the flow area of the flow meter and thus affect the measuring accuracy, and they may also hinder or attenuate the ultrasonic signals transmitted and received by the ultrasonic transducer, or affect the reflection of ultrasonic signals on the inner wall of the meter body. Therefore, the flow meter shall be inspected and cleaned regularly" (see 5.1 of Edition 2014);
f) Components for which temperature requirements are added include the meter body, field-mounted electronic facilities, and associated peripheral equipment, connecting cables, and ultrasonic transducer (see 5.3 hereof);
g) The length and diameter requirements for flow meters are changed, and the descriptions of equal-diameter and reduced-diameter flow meters and the requirements for inner diameter difference are added (see 7.2.4 hereof; 7.2.4 of Edition 2014);
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h) The following requirements are added: “The pressure tapping of the reduced flow meter shall be located within the reduced-diameter section, and the connecting pipe at the pressure tapping shall be marked with ‘Pm’ ” and “In case there are multiple ‘Pm’ pressure tappings, the difference of pressure readings at these pressure tappings at the maximum flow shall not exceed 100 Pa” (see 7.2.6 hereof; 7.2.6 of Edition 2014);
i) Modifications are made to the requirements for configuration and maintenance software, and for energy/calorific value display function, and function of reliable preservation of parameter settings and non-alterable event recording (see 7.5.2 hereof; 7.5.2 of Edition 2014);
j) Schematic diagrams for installation of ultrasonic flow meter for unidirectional and bidirectional measurements are added (see 8.2.1 hereof);
k) The following requirement is added: “The roughness (Ra) of inner surface of the upstream and downstream straight lengths adjacent to the flow meter should not be greater than 3.2 × 10-6 m” (see 8.2.4 hereof);
l) The followings are added: “If the insertion depth is greater than 1/3D, the thermometer sleeve needs to be subject to special design”, and “or other measures shall be taken to prevent the influence of ambient temperature on the measurement performance of the flow meter.” (see 8.2.5 hereof);
m) Requirements for series measurement are added (see 8.2.8 hereof);
n) Requirements for periodic inspection are added (see 8.3.2 hereof);
o) Requirements for offset inspection are added (see 8.3.3 hereof)；
p) The standard on which the calculation method in sound speed test is based is replaced with GB/T 30500 (see 9.2.3 hereof; 9.1.3 of Edition 2014);
q) The requirement for “Equation 7 for evaluating volume flow-rate measurement uncertainty subject to flow calibration under standard reference conditions” is modified (see 10.2.2 hereof; 10.4.2 of Edition 2014).
Attention is drawn to the possibility that some content of this document may involve patents. The issuing body of this document shall not be held responsible for identifying any or all such patent rights.
This standard was proposed by and is under the jurisdiction of SAT/TC 355 National Technical Committee on Petroleum and Natural Gas of Standardization Administration of China.
This document was issued in 2001 as the first edition, its first revision was issued in 2014, and this is the second revision.
Measurement of natural gas flow by gas ultrasonic flow meters
1 Scope
This standard specifies requirements on measuring performance, meter body, installation and maintenance, site verification test, as well as flow calculation method and measurement uncertainty estimation in connection with plug-in gas ultrasonic flow meters using transit-time difference method (hereinafter referred to as “flow meters”).
This document is applicable to the measurement of natural gas flow in gathering and transportation facilities, gas transmission pipelines, storage facilities, gas distribution systems, measurement systems of the users, standard facilities of measurement, and other application places.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 2624.2 Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full - Part 2: Orifice plates
GB/T 3836.1 Explosive atmospheres - Part 1: Equipment - General requirements
GB/T 3836.2 Explosive atmospheres - Part 2: Equipment protection by flameproof enclosures “d”
GB/T 3836.4 Explosive atmospheres - Part 4: Equipment protection by intrinsic safety “i”
GB/T 4208 Degrees of protection provided by enclosure (IP code)
GB/T 11062 Natural gas - Calculation of calorific values, density, relative density and Wobbe index
GB/T 13610 Analysis of natural gas composition - Gas chromatography
GB/T 17747 (all parts) Natural gas - Calculation of compression factor
GB/T 21446 Measurement of natural gas flow by means of standard orifice meter
GB/T 30500 Ultrasonic gas flow meter performance online audit - Method using speed of sound checking
GB/T 35186 Performance evaluation of measuring system for natural gas
JJG 1030 Ultrasonic flowmeters
SY/T 0599 Specification for sulfide stress cracking and stress corrosion cracking resistant metallic materials for natural gas surface facilities
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
transit-time difference method
method for the measurement of gas flow, which determines average flow velocity along acoustic path by transmit-time difference between two ultrasonic signals transmitted downstream and upstream within the same stroke of the flowing gas
[Source: GB/T 8423.4-2022, 4.1.25, modified]
3.2
ultrasonic transducer
component that converts acoustic energy into electrical signals or converts electrical signals into acoustic energy
Note: Ultrasonic transducers are usually installed in pairs and work at the same time.
[Source: GB/T 8423.4-2022, 4.1.22]
3.3
signal processing unit; SPU
electronic equipment composed of electronic components and microprocessor system, having the functions of receiving signals from ultrasonic transducer, processing measurement signals, and displaying, outputting and recording measurement results
Note: It is part of the flow meter.
3.4
meter body
pipe section for the tested gas to pass through, equipped with components such as ultrasonic transducers and couplings for pressure measurements, and specially manufactured to comply with requirements of relevant standards in all aspects
[Source: GB/T 8423.4-2022, 4.1.26]
3.5
acoustic path
actual transmission route of ultrasonic signals between a pair of transmitting and receiving ultrasonic transducers
[Source: GB/T 8423.4-2022, 4.1.27]
3.6
path length
L
straight length between end faces of a pair of ultrasonic transducers
Note: See Figure 1.
[Source: GB/T 8423.4-2022, 4.1.28, modified]
Key:
D——the measured inner diameter of the pipe;
L——the path length;
φ——the path angle;
TX1——the ultrasonic transducer 1;
TX2——the ultrasonic transducer 2;
X——the axial distance between ultrasonic transducer 1 and ultrasonic transducer 2.
Figure 1 Schematic diagram for geometrical relationship in plug-in measurement of gas ultrasonic flow
3.7
axial distance
X
projected length of the path length on the line parallel to the pipe axis
Note: See Figure 1.
[Source: GB/T 8423.4-2022, 4.1.29, modified]
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3.8
transmission angle; path angle
φ
included angle between the acoustic path and the pipe axis
Note: See Figure 1.
[Source: GB/T 8423.4-2022, 4.1.30, modified]
3.9
average flow velocity along acoustic path
gas flow velocity in the plane determined by the acoustic path and the flow direction
[Source: GB/T 8423.4-2022, 4.1.39]
3.10
mean axial fluid velocity
V
ratio of flowrate to cross-sectional area
[Source: GB/T 8423.4-2022, 4.1.40]
3.11
velocity distribution correction
kc
ratio of mean axial fluid velocity to average flow velocity along acoustic path
[Source: GB/T 8423.4-2022, 4.1.41]
3.12
zero-flow reading
maximum permissible flow velocity reading of the gas under static state
3.13
transition flowrate
qt
flowrate between the maximum and minimum flowrates
Note: It divides the flowrate range into two zones, namely "high zone (qt–qmax)" and "low zone (qmin–qt)", which have different maximum permissible errors.
[Source: GB/T 8423.4-2022, 4.1.4]
3.14
maximum peak-to-peak error; MPPE
difference between the maximum error point of upper limit and that of lower limit of the flow meter within the specified flowrate range
[Source: GB/T 8423.4-2022, 4.2.4, modified]
3.15
speed of sound deviation; SOS deviation
maximum relative deviation between the average speed of sound measured by the flow meter and the theoretical speed of sound
[Source: GB/T 8423.4-2022, 4.1.38]
3.16
metering package
package composed of the flow meter, and the auxiliary upstream and downstream straight lengths, temperature tapping, pressure tapping, and flow conditioner
[Source: GB/T 8423.4-2022, 3.3.17]
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Principle of measurement
4.1 Basic principle
4.2 Influencing factors of measuring accuracy
5 Working conditions
5.1 Natural gas quality
5.2 Pressure
5.3 Temperature
5.4 Flow range and flow direction
5.5 Velocity distribution
6 Measurement performance requirements
6.1 General requirements
6.2 Measurement performance requirements for multi-path gas ultrasonic flow meters
6.3 Measurement performance requirements for single-path gas ultrasonic flow meters
6.4 Effect of working conditions on measurement performance
7 Flow meters
7.1 Composition and basic requirements
7.2 Meter body
7.3 Ultrasonic transducers
7.4 Electronic components
7.5 Flow rate computer
8 Requirements for installation and maintenance
8.1 Factors influencing installation
8.2 Pipe configuration
8.3 Maintenance
9 Requirements for on-site validation test
9.1 General
9.2 Test contents and procedures
9.3 Test report
10 Methods for calculating flowrates and estimation on measurement uncertainty
10.1 Methods for calculating flowrates
10.2 Estimation on flowrate measurement uncertainty
Annex A (Informative) Basic principle for the measurement by gas ultrasonic flow meters
Annex B (Informative) Flow calibration of flow meters
Annex C (Normative) End-of-manufacturing test requirements
Annex D (Informative) Provided documents
Annex E (Informative) Generation of acoustic noise and prevention measures
Annex F (Informative) Performance verification test of flow meter and flow conditioner
Annex G (Informative) Inspection and assurance of on-site measurement performance of flow meter
Bibliography
Figure 1 Schematic diagram for geometrical relationship in plug-in measurement of gas ultrasonic flow
Figure 2 Summery of measurement performance requirements for multi-path gas ultrasonic flow meters
Figure 3 Schematic diagram for installation of ultrasonic flow meter for unidirectional measurement
Figure 4 Schematic diagram for installation of ultrasonic flow meter used for bidirectional measurement
Figure A.1 Diagram of turbulent flow velocity distribution in smooth pipe
Figure A.2 Exaggerated curvature diagram of the acoustic path
Figure A.3 Simple detection diagram for received pulses
Figure E.1 Diagram of installation for noise measurement
Figure G.1 Schematic diagram of relative SOS deviation curve of a 5-path flow meter during nitrogen dry calibration and flow calibration
Table E.1 Attenuation of noise by pipe elements at 200kHz
Table G.1 Examples of self-diagnostic information analysis
